Trick play using crt scan modes

ABSTRACT

Video frames of a performance are provided at times at a slower input rate and at other times at a faster input rate. A video display is automatically switched to a first display scan mode when receiving frames at the slower input rate, and switched to a second display scan mode when receiving frames at the faster input rate. The second display scan mode being different than the first display scan mode. For example, the display scan modes may have different frame rates or the first display mode may be progressive and the second display scan mode may be interlaced.

The invention relates to the field of video display with trick playmodes.

Recently CRT monitors with multiple scan modes have become more popular.Usually there are at least two scan modes. In the Americas, one scanmode has a 60 Hz scan rate for displaying 30 frames per second (60interlaced fields), and the other mode has a 120 Hz scan rate fordisplaying 60 frames per second (120 interlaced fields). In most of therest of the world the scan rates are 50 Hz and 100 Hz. The scan mode canusually be selected using buttons on the front of the monitor or byaccessing a menu. Often, when operated in the mode with the 60 Hz scanrate and interlaced frames, there is some barely detectable flickerespecially in a room that is brightly lit with fluorescent lighting. Onthe other hand, when operated in the mode with an 120 Hz scan rate,there may be distortions in brightness, contrast, or color because ofthe difficulty in aiming the electron gun of the CRT at such high scanrates. For this reason, monitors having duel 60/120 modes are oftenoperated at the 60 Hz mode rather then the faster mode.

For computing tasks 60 and 120 Hz frame display rates are convenientbecause computer hardware usually supports providing display frames atthese rates. However for video display, the frames are not necessarilyat these rates.

The MPEG video standard specifies several standard frame rates fornormal real-time display and includes a frame rate code that indicatesthe frame rate for normal real-time display. For movies the frame rateis 24 per second, and for American television the frame rate is usually30 per second (25 in most of the rest of the world). If a display devicesuch as a CRT has a display rate that is higher than the MPEG framerate, then the decoder can simply drop some frames. More commonly, ifthe MPEG frame rate is a lower rate then the frame rate of the display,then frames can be repeated or additional frames can be derived byaveraging between sequential frames.

Video sources such as VCR drives and DVD drives usually also provide fortrick play speeds. Common trick play speeds include forward and reverseplay at various multiples of the normal play speed such as ½×, 2×, 4×,8× and 16×. These trick play modes are often provided using the sameframe display rate and just dropping some of the frames or repeatingsome of the frames. For example, for 4× play, only every fourth frame isdisplayed so that three frames are dropped between each two successiveframes that are shown.

Those skilled in the art are directed to U.S. application Ser. No.09/281013 filed Mar. 30, 1999 (WO 00/59219 published Oct. 5, 2000) andWO 00/57241 published Sep. 28, 2000 which describe trick modeimplementations on display devices. Also, those skilled in the art aredirected to U.S. application Ser. No. 10/185,905 filed Jun. 28, 2002describing conversion of video formats to 120 Hz 4× interlaced format.These citations are hereby incorporated herein in whole by reference.

In the invention herein, a display device is provided which has multiplefixed predetermined display scan modes with corresponding frame displayrates that are independent of the average frame input rate andselectable at least between: a first mode and a second mode that issubstantially different than the first display rate. Video frames of avideo program are provided with a predetermined standard average inputrate that is selectable at least between: a slower average input rateand a faster average input rate that is substantially different than theslower input rate. The display scan mode of the display is selected soas to select the first mode when receiving frames at the faster inputrate and to select the second mode when receiving frames at the slowerinput rate.

The first display scan mode may have a higher frame rate, the advantageof this is that fast trick play modes have a less jerky appearance, whenfewer frames are dropped. The first mode may be a progressive displayscan mode and the second mode may be an interlaced display scan mode andthe display device may have a converter for converting progressiveframes at a fast rate to interlaced frames at a lower frame rate.

Additional aspects and advantages of the invention will become readilyapparent to those skilled in the art from the detailed description belowwith reference to the following drawings.

FIG. 1 illustrates the method of the invention for automaticallyproviding correspondence between the scan mode of a display device andthe input frame rate.

FIG. 2 illustrates an example video system of the invention forautomatically providing correspondence between a input frame rate andthe display scan mode.

FIG. 3 illustrates an alternative example video system of the inventionfor automatically providing correspondence between an input frame rateand the display scan mode.

FIG. 4 illustrates yet another example video system of the invention forautomatically providing correspondence between a input frame rate andthe display rate mode of a display device for trick mode play.

In the following descriptions of the drawings, the same labels indifferent figures indicate similar devices. For convenience, suchdevices will only be described in detail in relation to the earliestdescribed figure in which they appear.

FIG. 1 is a flow chart showing a specific example of the method 100 ofthe invention for automatically providing correspondence between a inputframe rate and the display rate mode of a display device for trick modeplay. In step 102 a display device is provided that has multiple fixedpredetermined display scan modes with corresponding frame display ratesthat are independent of the average frame input rate and selectable atleast between: a first scan mode and a second scan mode that issubstantially different than the first scan mode.

Most pixilated displays have a pixel refresh rate that defines a framedisplay rate. Typically those frame display rates are predeterminedfixed, hardware dependent rates. Those skilled in the art could modifyany such devices to provide multiple different frame display rates thatcould be automatically selected. In addition, common existing multi-modedisplay device include multi-mode CRTs, LCDs, plasma displays and LCOSprojectors. The display scan modes of those devices are commonlymanually selected, but those skilled in the art could modify suchdevices for automatic selection of mode depending on an indication ofthe rate at which frames are being provided. For example, the displaydevice could automatically detect the frame input rate or the displaydevice could receive a command from the video source indicating a changein the input rate, or the display device could receive a user inputcommand to change the input rate.

In step 104, video frames of a video program are provided. The programhas predetermined standard average input rates that are selectable atleast between: a slower average input rate and a faster average inputrate that is substantially different than the slower input rate.

The video frames could be provided by a video source such as a DVD driveor a digital VCR drive, or a magnetic disc drive (hard drive). A userinput device could be provided to select between predetermined averageinput rates at which the frames could be provide to the display. Theuser input could be, for example, a keyboard, a remote control, orbuttons on the front panel of the video source.

In step 106, the mode of the display device is automatically controlledto select the first mode with a when receiving frames at a faster inputrate and to select the second mode when receiving frames at a slowerinput rate.

The automatic control of the display device may be provided by adetector for determining the input frame rate and a processor forchanging the display scan mode depending on the input frame rate.Alternatively, the display device may receive a command from the sourceof the video frames to change the display scan mode depending on theselected input frame rate. Another possibility is that a user inputdevice may be provided, and the input of a command to select operationat a display scan mode may also control the selection of a input framerate.

The invention herein can be used in many different ways. The slowerframe input rate may constitute a normal play mode and the faster inputrate may constitute a fast motion mode. Alternatively, the slower inputrate may constitute a slow motion mode and the faster input rateconstitute normal real-time play. Also, both input rates may be fordifferent slow motion modes or both input rates may be for differentfast motion modes.

For either the slower or faster frame rates, if the frame input rate isslower than the frame display rate then at least some received frameswill have to be repeated. Also, for either the slower or faster framerates, if the frame input rate is higher than the frame display ratethen some frames will have to be dropped.

Usually input rates for slow motion trick modes are simply integerdivisions of the normal real-time frame input rate (positive integersfor forward modes and negative integers for reverse modes). Thissimplifies the implementation of slow motion, because each frame can berepeated the same number of times. Similarly the input rates for fastmotion trick play modes are simply integer multiple of the normalreal-time frame input rate. This simplifies the implementation of fastmotion trick play because then the same number of frames can be droppedbetween each frame that is displayed.

It is convenient if the faster input rate is twice as fast as the slowerinput rate, because for most current multi-mode display devices thereare two modes in which one is twice as fast as the other.

To simplify implementation and minimize jerkiness if the slower displayrate were equal to the slower input rate, because then, every framewould simply be displayed one time, and there would be no repeated ordropped frames. Similarly, it would simplify implementation and minimizejerkiness if the faster display rate were equal to the faster inputrate, because then, every frame would simply be displayed one time, andthere would be no repeated or dropped frames.

For example, the input frames in both the slower and faster input ratemay be provided in a progressive scan format with he first display scanmode at a 25 Hz or 30 Hz progressive scan mode and the second displayscan mode at 50 Hz or 60 Hz progressive scan mode.

Alternatively, the input frames in both the slower and faster input ratemay be in a 2× interlaced scan format with the first display scan mode,a 50 Hz or 60 Hz 2× interlaced scan mode, and the second display scanmode, a 100 Hz or 120 Hz 2× interlaced scan mode.

FIG. 2 illustrates an example embodiment of a video system 120 of theinvention in which the mode of a display device is automaticallycorresponds to the average input frame rate provided by the videoprogram source. In this example of a specific embodiment, in videoprogram source 122, the average frame rate of a medium drive 124 isselected using user input device 126.

The medium drive may be an optical medium drive such as a DVD drive or avideo CD drive or it may be a digital VCR tape drive, or a magnetic harddisc drive containing a video program. The medium drive is capable ofproviding video frames at a normal real-time play rate for the programor at trick play rates that are slower or faster than the normal playrate.

The user input may be buttons on the front panel of the video mediumdrive or a remote control capable of communicating with the video mediumdrive, or the user input may be a computer keyboard that communicateswith the video medium drive through a personal computer and/or homenetwork.

The video program source 122 provide frames to a display device 130. Thedisplay device includes a multi-mode display 132 that receives theframes through buffer 134. A processor 136 detects the input frame rateof the buffer 134, and automatically selects the display scan mode ofthe multi-mode display depending on the input frame rate.

The multi-mode display may be a CRT which is capable, for example, ofdisplaying frames at a rate of either 30 frames or 60 frames per second.Alternatively the muti-mode display may be an LCD screen, a plasmadisplay screen, or a display projector.

The display device displays frames at a faster rate when frames arereceived at a fast average rate, and the display device displays framesat a slower rate when frames are received at a slower average rate. Forexample, an MPEG movie may have a normal play input rate of 24 framesper second and in response to this frame rate the display will displayframes at the rate of 30 frames per second. In order to display moreframes than are received, the display device will occasionally displaysome of the frames twice. Buffer 134 stores the frames so that they canbe displayed multiple times for slow trick play modes. When the videoprogram source goes into a fast motion trick mode such as 4 times normalspeed (called 4×) (60 frames per second), then the display device willdetect the faster frame rate and switch the operating mode to 60 framesper second. The display device will have to occasionally drop some ofthe video frames, but will not ever have to drop two frames in a row.For programs with normal display rates of 24 or 30 frames per second,Display of 4× speed on a display operating at 60 frames per secondappears smooth, whereas even 2× speed appears jerky on a displayoperating at 30 frames per second.

Alternatively, when the user inputs a command through user input 126, toinitiate a fast motion trick play mode, then video medium drive 124provides a command to the display device to automatically switch thedisplay device to operate in a mode for displaying frames at a fasterrate. Processor 136 receives the command and selects a faster rate modefor the multi-mode display 132. In this case there is no need forprocessor 136 to detect the input frame rate.

converter 128 converts the input frames as required for the displaydevice. For a slow motion trick play mode the converter may repeatframes or for a fast motion trick play mode the converter may dropframes or combine frames so as to provide the frame rate required forthe display device scan mode. The converter may convert frames formattedfor progressive scan to frames formatted for interlaced scans, forexample, to reduce the frame rate. The conversion of the converter isalso controlled by the user input command.

For example, multiple frames with a progressive scan format may becombined by combining some of the lines of each frame together to form acombined frame with a progressive scan format. Thus n frames may becombined using every n th line of each of the n frames to form thecombined frame, every n th line beginning at a different line for eachdifferent frame. For example, a pair of frames are combined by combiningthe odd lines of one frame with the even lines of the other frame.

In another example, multiple frames with a progressive scan format maybe combined by dropping lines of each frame to form a combined framewith an interlaced format. Thus, n frames may be combined by droppingall the lines except every n th line of each frame, every n th linebeginning at a different line position in each different frame of the nframes.

In yet another example, multiple frames with an interlaced format may becombined by dropping one or more fields of each frame to form a combinedframe with an interlaced format. For example a different field from eachframe can be combined to form the combined frame.

In yet another example, multiple frames with an interlaced scan formatmay be combined by dropping lines of each frame to form a combined frameof interlaced format. Thus, n frames can be combined by dropping all thelines except every n th line of each field, every n th line beginning ata different line position in each different frame of the n frames.

In FIG. 3, Display device 142 includes processor 142 communicating withuser input 126. When a user inputs a command through user input 126 toselect a fast motion trick play mode, then processor 142 automaticallyselects a display scan mode with a higher frame display rate and theprocessor sends a signal to video program source 124 to automaticallyprovide frames at a faster frame rate. In this case converter 128 isprovided as part of the display device.

In FIG. 4, user input device 150, communicates directly with both thevideo program source 122, converter 128, and the display device 130.When the user inputs a command to operate the system in a fast motiontrick play mode, then the same command automatically causes the videoprogram source 122 to provide frames at a higher input rate and thedisplay device 130 to switch to a higher display rate.

The invention has been described above in relation to specific exampleembodiments. Those skilled in the art will know how to modify theseexample embodiments within the scope of the invention herein. Theinvention is only limited by the following claims.

1. A method comprising: at times providing video frames of a performanceat a slower input rate; at other times providing video frames of theperformance at a faster input rate; switching a video display to displayframes in first display scan mode when receiving frames at the slowerinput rate; and switching the video display to display frames in asecond display scan mode when receiving frames at the faster input rate,the second display scan mode being different than the first display scanmode.
 2. The method of claim 1, wherein: the slower input rate is equalto a normal play rate of the video performance, and the faster play rateis for a fast motion trick mode.
 3. The method of claim 1 wherein theframes received in both the slower and faster input rate are in aprogressive scan format; the first display scan mode is a 25 Hz or 30 Hzprogressive scan mode; and the second display scan mode is a 50 Hz or 60Hz progressive scan mode.
 4. The method of claim 1 wherein: the framesreceived in both the slower and faster input rate are in a 2× interlacedscan format; the first display scan mode is a 50 Hz or 60 Hz 2×interlaced scan mode; and the second display scan mode is a 100 Hz or120 Hz 2× interlaced scan mode.
 5. The method of claim 1 furthercomprising repeating the display of frames received at the slower inputrate to provide a required frame rate for the first display scan mode.6. The method of claim 1 further comprising dropping some of the framesreceived at the higher input rate to provide a required frame rate forthe second display scan mode.
 7. The method of claim 1 furthercomprising combining frames received at a faster input rate intocombined frames to provide a required frame rate for the second displayscan mode.
 8. The method of claim 1, wherein: the method furthercomprises detecting the input rate; and automatically selecting thedisplay scan mode depending on the detected input rate.
 9. The method ofclaim 1, wherein: the method further comprises receiving a user inputcommand to change the input rate; and changing the input rate inresponse to the user input command to change the input rate.
 10. Themethod of claim 1, wherein: the method further comprises receiving auser input command to change the input rate; and changing the displayscan mode in response to the user input command to change the inputrate.
 11. The method of claim 1, wherein the received frames areprovided by a medium player that provides video frames at a controllableaverage input rate.
 12. The method of claim 11, wherein the mediumplayer is selected from a DVD drive, a digital VCR, and a magnetic discdrive.
 13. The method of claim 11, wherein the medium player includesuser input apparatus for providing a command to change the average inputrate.
 14. The method of claim 1, wherein the display is a CRT and thedifferent display scan modes are selected from: a progressive scan 30 Hzmode, a progressive scan 60 Hz mode, a 2× interlaced 60 Hz mode, a 2×interlaced 120 Hz mode, a 4× interlaced 120 Hz mode and a 4× interlaced240 Hz mode.
 15. The method of claim 1, wherein: the display is a CRTand the different display scan modes are selected from: a progressivescan 25 Hz mode, a progressive scan 50 Hz mode, a 2× interlaced 50 Hzmode, a 2× interlaced 100 Hz mode, a 4× interlaced 100 Hz mode and a 4×interlaced 200 Hz mode.
 16. A method comprising: at times providingvideo frames at a slower input rate; displaying the frames received atthe slower input rate; at other times providing video frames at a higherinput rate; combining the frames received at the higher input rate intocombined frames at the slower frame rate; and displaying the combinedframes at the slower frame rate.
 17. The method of claim 16 whereinmultiple frames with a progressive scan format are combined by combiningsome of the lines of each frame together to form a combined frame with aprogressive scan format.
 18. The method of claim 17 wherein n frames arecombined using every n th line of each of the n frames to form thecombined frame, every n th line beginning at a different line for eachdifferent frame.
 19. The method of claim 18 wherein a pair of frames arecombined by combining the odd lines of one frame with the even lines ofthe other frame.
 20. The method of claim 16 wherein multiple frames witha progressive scan format are combined by dropping lines of each frameto form a combined frame with an interlaced format.
 21. The method ofclaim 20 wherein n frames are combined by dropping all the lines exceptevery n th line of each frame, every n th line beginning at a differentline position in each different frame of the n frames.
 22. The method ofclaim 16 wherein multiple frames with an interlaced format are combinedby dropping one or more fields of each frame to form a combined framewith an interlaced format.
 23. The method of claim 22 wherein adifferent field from each frame is combined to form the combined frame.24. The method of claim 16 wherein multiple frames with an interlacedscan format are combined by dropping lines of each frame to form acombined frame of interlaced format.
 25. The method of claim 24 whereinn frames are combined by dropping all the lines except every n th lineof each field, every n th line beginning at a different line position ineach different frame of the n frames.
 26. The method of claim 16 whereinthe slower input rate has the same frame rate as the slower frame rate.27. A video player comprising: a display device (132) having multiplefixed predetermined display scan modes with corresponding display ratesthat are independent of the average frame input rate and selectable atleast between: a first display scan mode and a second display scan modethat is substantially different than the first display scan mode; aninput (122) for video frames of a video program with an predeterminedstandard average input rate that is selectable at least between: aslower average input rate and a faster average input rate that issubstantially different than the slower input rate; and means (136) forselecting the first display scan mode when receiving frames at theslower input rate and for selecting the second display scan mode whenreceiving frames at the faster input rate.
 28. The video player of claim18, wherein the slower input rate is equal to a normal play rate of thevideo performance, and the faster play rate is for a fast motion trickmode.
 29. The video player of claim 18, wherein: the frames received inboth the slower and faster input rate are in a progressive scan format;the first display scan mode is a 25 Hz or 30 Hz progressive scan mode;and the second display scan mode is a 50 Hz or 60 Hz progressive scanmode.
 30. The video player of claim 18, wherein: the frames received inboth the slower and faster input rate are in a 2× interlaced scanformat; the first display scan mode is a 50 Hz or 60 Hz 2× interlacedscan mode; and the second display scan mode is a 100 Hz or 120 Hz 2×interlaced scan mode.
 31. The video player of claim 18, wherein thereceived video player further comprises means (128) for converting thevideo frames including repeating the display of frames received at theslower input rate to provide a required frame rate for the first displayscan mode.
 32. The video player of claim 18, wherein the video playerfurther comprises means (128) for converting the received video framesincluding dropping some of the frames received at the higher input rateto provide a required frame rate for the second display scan mode. 33.The video player of claim 18, wherein the video player further comprisesmeans for converting the received video frames including combiningframes received at a faster input rate into combined frames to provide arequired frame rate for the second display scan mode.
 34. The videoplayer of claim 18, wherein the video player further comprises means(136) for detecting the input rate; and the selecting means selects thedisplay scan mode depending on the detected input rate.
 35. The videoplayer of claim 18, wherein: the video player further comprises a userinput (126, 150) for providing a command to change the input rate; andmeans (142) for changing the input rate in response to the user inputcommand to change the input rate.
 36. The video player of claim 18,wherein: the video player further comprises a user input (126) forproviding a command to change the input rate; and means (142) forchanging the display scan mode in response to the user input command tochange the input rate.
 37. The video player of claim 29, wherein thevideo player further comprises a video medium reader (124) for providingthe video frames of a video program with a controllable average inputrate.
 38. The video player of claim 30, wherein the video medium readerplayer is selected from a DVD drive, a digital VCR, and a magnetic discdrive.
 39. The video player of claim 30, wherein the video medium playerincludes a user input for providing a command to change the averageinput rate.
 40. A display device comprising: a video display fordisplaying video frames at one of a multitude of different predetermineddisplay scan rates; a user input device for selecting a frame rate and acorresponding display scan mode of the video device from among multipledifferent predetermined display scan modes, the video frame display rateof the display device depending on the display scan mode; and atransmitter to transmit the selected frame rate to a video source toprovide frames at an average rate depending on the selection.